I agree with Dave, familiarity with a version results in being comfortable with the development environment. I never used the Menu system or the Ribbon, naff, naff, the other change in Access 2007 was images being able to be stored in their native formats, rather than OLE. I know this sounds a little stupid, but I've had to ask the forum how to find something in Access 2007.
I remember an argument justifying an upgrade from Word 1997, 1997 has 100 commands and 2003 about 1000.
I don't think it matters what upgrade path you take, Bob Larson reckons Access 14 has some nice features so we await both this version and Windows 7.
Simon